In the principle of the lever, the so-called proximal-pivot type scissors in which the force point is located between the load and pivot points are generally known. As for the forms of such scissors belonging to the simplest or handiest class, one shown in FIGS. 13-15 may be said to be typical.
In this form of scissors, as will be later described, the bent proximal end portion of a spring steel member bent in elongated horizontally U-shape is used as a pivot point, while the opposed front end portions are used as a pair of vertically opposed cutting blades, which are maintained normally opened and which, in use, are closed by the user grasping the scissors by hand so as to shear an object by the rubbing action of the cutting edges.
In this form, however, the thickness of the spring steel member is not uniform as a whole and instead the bent proximal end portion serving as the pivot point is thinned and flattened in sheet form for the purpose of imparting springiness thereto and it is also necessary to likewise thin and flatten the opposed front end portions into sheet form at right angles to said proximal end portion. Further, the front end portions must be specially machined to provide sharp cutting edges. For this reason, the manufacture of the scissors is still complicated, making it impossible to expect the effect of mass-production to the greatest extent.
Further, since the springy steel member is simply bent to bring the cutting edges into opposed relation for rubbing action, the cutting edges tend to move laterally away from each other when an object is to be cut, so that the object often remains clamped in a clearance between the rubbing cutting edges. Such phenomenon becomes more noticeable as the cutting edges are dulled in years of use or when the thickness of an object to be cut changes. To prevent this, it is necessary for the user to manually impart frictional urging forces in a lateral direction from the opposite sides so as to force the cutting edges to rub each other. Thus, it is clear that the lightness of action is decreased.
Further, the front end portions of the spring steel member having the cutting edges which are adapted to rub each other are left exposed, a fact which, coupled with the fact that the cutting edges tend to move laterally away from each other, makes the scissors very dangerous to use.